1. Field of the Invention
The present invention relates to evaluation systems and evaluation methods, and more particularly to an evaluation system and an evaluation method that obtains a photoelectric conversion signal by photoelectrically detecting an area subject to detection, which includes a detection subject on an object, and evaluates a search operation of the detection subject that uses the photoelectric conversion signal.
2. Description of the Related Art
Recently, in a process of manufacturing devices such as semiconductor devices, exposure apparatuses by a step-and-repeat method or a step-and-scan method, wafer probers, laser repair apparatuses or the like are used. In these apparatuses, each of a plurality of shot areas arranged on a substrate need to be positioned (aligned) extremely precisely with a predetermined datum point (e.g. a processing operation point of each apparatus) in a stationary coordinate system that sets a moving position of the substrate (an orthogonal coordinate system that sets a position coordinate of a stage holding the substrate, that is, a stage coordinate system).
In an exposure apparatus, in particular, 10 or more layers of circuit patterns (reticle patterns) are overlaid and transferred onto a substrate (hereinafter referred to as ‘wafer’), and in the case the overlay accuracy between layers is poor, inconveniences may arise in the quality of the circuit. In such a case, the chip does not satisfy a desired quality, and the chip becomes defective in the worst case, which reduces the yield. Accordingly, in the exposure apparatus, an alignment mark is arranged in advance in each of a plurality of shot areas (areas where circuit patterns are transferred) on a wafer, and a position coordinate of the alignment mark in a stage coordinate system that sets movement of a stage holding the wafer is detected. After that, wafer alignment is performed in which an individual shot area on the wafer is aligned with a reticle pattern based on a positional relation (measured beforehand) between the position coordinate of the mark and the known reticle pattern.
In the wafer alignment, a waveform data that represents photoelectric conversion signals corresponding to areas on the wafer including the alignment marks is obtained, and in the obtained waveform data, a section corresponding to the alignment marks are searched for and the positions where it is recognized that the alignment marks exist are detected as the position coordinates of the alignment marks in the stage coordinate system.
More specifically, by searching the waveform data, several positions (potential positions) are extracted that are highly likely to be positions of the alignment marks from the waveform data based on characteristics of the alignment marks, and the correlativity between a template waveform when matching the template waveform of the mark with each of a plurality of potential positions and the waveform data corresponding to the template waveform is obtained. Based on the correlativity, the judgment is made of whether the marks could be recognized or not, and out of the positions where it is judged that the marks were recognized, the position where the correlativity is highest is detected as the position of the mark.
Meanwhile, in the case the waveform data is searched and the above correlativity is equal to or less than a predetermined level at all the potential positions, a so-called mark detection error is generated since the marks could not be recognized. As the causes for not being able to recognize the marks at any potential position, various causes can be considered. For example, it is a matter of course that the marks cannot be recognized at times due to a noise component included in the waveform data, however, the case can also be considered where values of processing parameters that set a mark recognition operation such as a design value of a mark width required for performing the mark recognition operation are not appropriately set. In this case, by re-setting the processing parameters to the appropriate values, the position of the mark can be searched for without generating unnecessary mark detection errors.
From the point of view as described above, the necessity is increasing for an environment where analysis and evaluation of the mark search operation with respect to the waveform data is performed so that the cause of not being able to recognize the marks can be specified and the processing parameters can be adjusted. However, due to the large number of the above processing parameters existing, it is difficult to make the setting values of the processing parameters be appropriate if the processing parameters are randomly adjusted, and it also requires time.